1. Field of the Invention
This invention is directed to an aerosol solvent weld cement composition, a dispensing system including an omnidirectional female valve for dispensing the composition, and a method of joining pipe using the composition.
2. Description of the Related Art
Plastic pipe has become increasingly used in a wide variety of applications, such as in water transmission networks, residential plumbing, and in the construction of a wide variety of structures having no relation to water transmission. Plastic pipe continues to replace ceramic and metal pipe in a variety of applications owing to its reduced weight, lower cost, and resistance to cracking under stress. Suitable plastics commonly used for pipes are chloropolyvinylchloride, known as CPVC, polyvinylchloride, known as PVC, or poly(acrylonitrile-butadiene-styrene), known as ABS. Of these, the PVC is the most common.
It is known in the art to join sections of plastic piping together in the formation of an elongated plastic pipe. Solvent weld cement has been used as a bonding agent in the joining of sections of plastic pipe. This agent softens the plastic surfaces to which it is applied and, when the surfaces harden, they are chemically bound together.
U.S. Pat. No. 5,336,351, issued to Meyers, discloses the use of solvent weld glue (or cement) to join pieces of plastic pipe. In this disclosure, a male end of a first section of plastic pipe is fitted with a flexible pipe connector made of low density polyethylene to form multiple receiving means on the outer surface. Solvent weld cement is applied to the receiving means and the thus-treated male end is inserted into the female end of a second section of plastic pipe. This method requires additional material, thus adding to the expense of construction. Also, if the work is being performed in confined areas, the attachment of the flexible pipe connector to the male end of the pipe would add frustration and labor costs to the procedure. The Meyers disclosure does not reveal the composition of the solvent weld cement or the method of application of the solvent weld cement to the flexible pipe connector.
King, Sr., in U.S. Pat. No. 4,687,798, reveals the use of a solvent weld cement wherein the improvement is an added ingredient in the solvent. The solvent weld cement is useful for the purpose of joining pieces of PVC. The use of solvent weld cements in the joining of plastic pipes is mentioned in this patent. The compositions of the King, Sr. formulation are stored and used in liquid form. The conventional method of using solvent weld cement compositions is to apply them with a brush or cloth to the pipes to be joined. This involves the use of an open container of the composition at the work site. Whether laying plastic pipes in trenches or in buildings under construction, the conditions for using an open container of liquid are far from ideal in that there is little open room. In such environments, the pipe layer has no convenient location where an open solvent weld cement container can be placed. During the process of installing pipes in trenches, the solvent weld cement container typically is placed either in the trench or alongside the top of the trench. Since the container may be knocked or kicked over, there is risk of a resultant loss of solvent weld cement, contamination of the soil with hazardous substances, and attendant loss of time and productivity. Also, there is the risk of contamination of the solvent weld cement by dirt, debris, or water at the work-site, which can adversely affect the efficiency of the solvent weld cement.
There are additional problems associated with the use of existing liquid solvent weld cements which are applied to the plastic pipes to be joined by use of a brush or cloth, This mode of application is normally messy, especially in cramped areas. Also, this mode of application often does not result in the desired uniformity of coverage. Thus, this method may fail to provide an effective amount of cement in some areas while other areas may contain too much, causing possible failure of the joint, waste, and mess.
Another drawback associated with liquid solvent weld cements is that they typically do not allow the installer enough time to properly align the abutting plastic pipes because the cement sets up in only three to five seconds and produces a weld that cannot be altered. Thus, it is desirable to have a solvent weld cement which can be applied to plastic pipe in such a manner that set-up time is extended to give the installer enough time to properly align the plastic pipe segments and be assured that the joint is proper.
Smrt et al, in U.S. Pat. No. 5,453,219, teaches an aerosol container containing a composition comprising an abrasive grit and a binder solution. The binder solution, which is suitable for affixing the grit onto a surface includes a polymeric resin, a solvent, and a liquid propellant. Upon being sprayed onto a surface, the solvent evaporates and the polymeric resin adheres the abrasive grit to the surface. The patent identifies the valve as being a standard SV-78 valve and the actuator as being a standard actuator.
It has been determined that in the spraying of paint, adhesives, and undercoatings from pressurized aerosol containers, the use of a male valve is inappropriate as male valves demonstrate a tendency to clog or plug, thereby rendering the aerosol container inoperative. The use of female valves for polymers has, until now, been limited to containers which are held upright. Such valves are less than ideal for the task of connecting plastic pipe as this task requires the sprayed composition to approach the pipe from all angles. Until now, an omnidirectional female valve has not been available to the art, and this has required physical gyrations by the user if anything other than surfaces easily sprayed by an upright container needed to be sprayed.
It can thus be seen that there exists a need for an aerosol composition having a solvent, a polymeric solvent weld cement material, and a propellant in a pressurized aerosol container wherein the container can be used in any position, the contents do not clog the valve, and the contents do not erode the container.